Storage devices commonly implement data replication operations using local and remote virtual library storage (VLS) for data recovery, also commonly referred to as “automigration” or “tape caching.” Automigration automatically mirrors virtual “tapes” on a local VLS to a remote device (either another VLS or a physical library).
A user may want to have different retention times for backup data on the local and remote libraries. For example, the user may want to store one month of backup data locally while storing six months of backup data at the remote library. However, strict identity between the local and remote libraries needed to implement automigration operations prohibits different retention times. By definition, strict identity or having the same data on both the local and remote libraries, necessitates the same retention time for both devices.
It may be possible to implement an out-of-band application programming interface (API) between the backup application and the virtual library (e.g. using the SMI-S or NDMP protocols) to allow the backup application to control the copy processes between the two virtual libraries. By allowing the backup application to control the copy processes, the local and remote tapes may be managed independently (e.g., have different barcodes and therefore be recognized as two different tapes by the backup application). However, this scheme would require significant changes to the backup application to support the API. Most if not all commercially available backup applications do not have this capability.